Polishing apparatus

ABSTRACT

A polishing apparatus is used for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and allows a polishing pad to be automatically replaced without stopping rotary or circulatory motion of a polishing table. The polishing apparatus comprises a polishing table for making rotary or circulatory motion, a top ring vertically movably disposed above the polishing table for removably holding a workpiece to be polished, a pair of rolls rotatable about their own axes and movable in unison with the polishing table and a polishing pad which is wound on one of the rolls and supplied over an upper surface of the polishing table toward the other of the rolls.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a polishing apparatus forpolishing a workpiece such as a semiconductor wafer to a flat mirrorfinish, and more particularly to a rotary-type polishing apparatus whichallows a polishing pad to be automatically replaced without stoppingrotary or circulatory motion of a polishing table.

[0003] 2. Description of the Related Art

[0004] Recent rapid progress in semiconductor device integration demandssmaller and smaller wiring patterns or interconnections and alsonarrower spaces between interconnections which connect active areas. Oneof the processes available for forming such interconnection isphotolithography. Though the photolithographic process can forminterconnections that are at most 0.5 μm wide, it requires that surfaceson which pattern images are to be focused by a stepper be as flat aspossible because the depth of focus of the optical system is relativelysmall.

[0005] It is therefore necessary to make the surfaces of semiconductorwafers flat for photolithography. One customary way of flattening thesurfaces of semiconductor wafers is to polish them with a polishingapparatus, and such a process is called Chemical Mechanical Polishing(CMP) in which the semiconductor wafers are chemically and mechanicallypolished while supplying a polishing liquid comprising abrasive grainsand chemical solution such as alkaline solution.

[0006] In a manufacturing process of a semiconductor device, a thin filmis formed on a semiconductor device, and then micromachining processes,such as patterning or forming holes, are applied thereto. Thereafter,the above processes are repeated to form thin films on the semiconductordevice. Recently, semiconductor devices have become more integrated, andthe structure of semiconductor elements has become more complicated. Inaddition, the number of layers in multilayer interconnections used for alogical system has been increased. Therefore, irregularities on thesurface of the semiconductor device are increased, so that the stepheight on the surface of the semiconductor device becomes larger.

[0007] When the irregularities of the surface of the semiconductordevice are increased, the following problems arise. The thickness of afilm formed in a portion having a step is relatively small. An opencircuit is caused by disconnection of interconnections, or a shortcircuit is caused by insufficient insulation between the layers. As aresult, good products cannot be obtained, and the yield is lowered.Further, even if a semiconductor device initially works normally,reliability of the semiconductor device is lowered after a long-termuse.

[0008] Thus, in the manufacturing process of a semiconductor device, itis increasingly important to planarize the surface of the semiconductordevice. The most important one of the planarizing technologies ischemical mechanical polishing (CMP). In the chemical mechanicalpolishing, a polishing apparatus is employed. While a polishing liquidcontaining abrasive particles such as silica (SiO₂) therein is suppliedonto a polishing surface such as a polishing pad, a substrate such asemiconductor wafer is brought into sliding contact with the polishingsurface, so that the substrate is polished.

[0009]FIGS. 16 and 17 of the accompanying drawings show a conventionalpolishing apparatus for carrying out a CMP process. As shown in FIGS. 16and 17, the conventional polishing apparatus comprises a polishing table102 having a polishing pad (polishing cloth) 100 attached to its uppersurface, a motor 104 for rotating the polishing table 102, and avertically movable top ring 106 for holding a substrate W such as asemiconductor wafer with its surface, to be polished, facing thepolishing table 102. While the polishing table 102 and the top ring 106are being rotated independently about their own axes, the substrate W ispressed against the polishing pad 100 under a constant pressure by thetop ring 106, and a polishing liquid is supplied from a nozzle (notshown) to the polishing pad 100, thereby polishing the surface of thesubstrate W to a flat mirror finish. The polishing liquid comprises fineabrasive particles of silica or the like suspended in an alkalinesolution or the like. The substrate W is polished by a chemicalmechanical polishing action which is a combination of a chemicalpolishing action performed by the alkaline solution and a mechanicalpolishing action performed by the abrasive particles of silica or thelike.

[0010] The polishing pad 100 is usually regenerated by a dresser whichcomprises a nylon brush, diamond particles, or the like. When thepolishing pad 100 is worn to the extent that its polishing capabilitycan no longer be restored by the dresser, the polishing pad 100 isreplaced with a new one.

[0011] The polishing pad 100 is generally attached to the upper surfaceof the polishing table 102 by an adhesive tape. For replacing thepolishing pad 100 with a new one, it is necessary to temporarily stopthe CMP process, and a skilled operator is required to peel off thepolishing pad 100 and attach a new polishing pad 100 to the polishingtable 102.

[0012]FIG. 18 of the accompanying drawings shows another conventionalpolishing apparatus for eliminating the above drawbacks. The polishingapparatus shown in FIG. 18 has a polishing pad 100 attached to apolishing table 102 under vacuum developed by a vacuum attractionsection 108 provided in the polishing table 102. Since the polishing pad100 is removed from the polishing table 102 by releasing the vacuum, thepolishing pad 100 can easily and quickly be replaced with a new one.However, replacing the polishing pad 100 needs to temporarily stop theCMP process because it cannot be replaced while the polishing table 102is rotating.

[0013] Still another conventional polishing apparatus is shown in FIG.19 of the accompanying drawings. In FIG. 19, a polishing table 110 isfixed in position, and a pair of rolls 112, 114 are rotatably disposedone on each side of the polishing table 110. An elongate polishing pad100 wound onto the roll 112 is continuously fed at a constant speedalong the upper surface of the polishing table 110 and beneath thesubstrate W toward the other roll 114 onto which the polishing pad 100is wound. The substrate W is polished by the elongate polishing pad 116as it travels over the polishing table 110 in one direction. Theprinciples of the polishing apparatus shown in FIG. 19 are notapplicable to the rotary-type polishing apparatus in which the polishingtable makes rotary or circulatory motion.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of the present invention to provide arotary-type polishing apparatus which has a polishing table that makesrotary or circulatory motion and which allows a polishing pad to beautomatically replaced without stopping a CMP process.

[0015] Another object of the present invention is to provide a polishingapparatus which has a polishing table that makes predetermined motionand which allows a polishing pad to be automatically replaced withoutstopping a CMP process.

[0016] According to the first aspect of the present invention, there isprovided a polishing apparatus comprising: a polishing table for makingrotary or circulatory motion; a top ring vertically movably disposedabove the polishing table for removably holding a workpiece to bepolished; a pair of rolls rotatable about their own axes and movable inunison with the polishing table; and a polishing pad which is wound onone of the rolls and supplied over an upper surface of the polishingtable toward the other of the rolls.

[0017] Even when the polishing table is in rotary or circulatory motion,the polishing pad can be transported from one of the rolls over theupper surface of the polishing table toward the other roll by a distancecorresponding to a region of the polishing pad that has been used topolish workpieces. The used region of the polishing pad can thusautomatically be replaced with a new region thereof.

[0018] In a preferred aspect of the present invention, the polishingtable has an attraction section for attracting and holding the polishingpad to the polishing table.

[0019] In a preferred aspect of the present invention, the polishingapparatus further comprises the roll motor connected to at least theother of the rolls, the roll motor being controllable in a wireless orwired fashion. When a signal is transmitted to the roll motor toenergize the roll motor to rotate the rolls, the used region of thepolishing pad can automatically be replaced with a new region thereof.

[0020] In a preferred aspect of the present invention, the polishing padcomprises one of a polyurethane foam pad, a swayed type pad, and a fixedabrasive pad comprising abrasive particles embedded therein.

[0021] In a preferred aspect of the present invention, the polishingapparatus further comprises a sensor for detecting surface roughness ofthe polishing pad.

[0022] In a preferred aspect of the present invention, the polishingapparatus further comprises a sensor for detecting surface roughness ofthe polishing pad; and the roll motor is energized on the basis ofdetection signal of the sensor.

[0023] In a preferred aspect of the present invention, the polishing padcomprises a plurality of polishing pads which are divided along atake-up direction of the polishing pad.

[0024] According to the second aspect of the present invention, there isprovided a polishing apparatus comprising: a polishing table for makingpredetermined motion; a top ring vertically movably disposed above thepolishing table for removably holding a workpiece to be polished; apolishing pad supply device for holding an elongate polishing pad andsupplying the polishing pad therefrom; and a polishing pad holdingdevice for holding the polishing pad supplied from the polishing padsupply device and placing the polishing pad such that the polishing padmake predetermined motion integrally with the polishing table.

[0025] According to the second aspect of the present invention, thepolishing pad is supplied from the polishing pad supply device, and thesupplied polishing pad is held by the polishing pad holding device andplaced in a stretched state on the polishing table. Thus, even if thepolishing table is in motion, the used region of the polishing pad canthus automatically be replaced with a new region of the polishing pad.

[0026] In a preferred aspect of the present invention, the polishing padsupply device comprises a supply roll onto which the elongate polishingpad is wound.

[0027] In a preferred aspect of the present invention, the polishing padholding device comprises a take-up roll onto which the elongatepolishing pad is to be wound.

[0028] In a preferred aspect of the present invention, the polishingtable has an attraction section for attracting and holding the polishingpad to the polishing table.

[0029] In a preferred aspect of the present invention, the polishingapparatus further comprises a roll motor connected to the take-up roll,the roll motor being controllable in a wireless or wired fashion.

[0030] In a preferred aspect of the present invention, the predeterminedmotion of the polishing table is one of rotary motion, circulatorymotion, and linear reciprocating motion.

[0031] According to the third aspect of the present invention, apolishing table for making predetermined motion; and a top ringvertically movably disposed above the polishing table for removablyholding a workpiece to be polished; a polishing pad supply device forholding an elongate polishing pad and supplying the polishing padtherefrom; a polishing pad holding device for holding the polishing padsupplied from the polishing pad supply device and placing the polishingpad such that the polishing pad make predetermined motion integrallywith the polishing table; and a sensor for detecting surface roughnessof the polishing pad.

[0032] According to the fourth aspect of the present invention, apolishing table for making predetermined motion; a top ring verticallymovably disposed above the polishing table for removably holding aworkpiece to be polished; a polishing pad supply device for holding anelongate polishing pad and supplying the polishing pad therefrom; apolishing pad holding device for holding the polishing pad supplied fromthe polishing pad supply device and placing the polishing pad such thatthe polishing pad make predetermined motion integrally with thepolishing table; and a brush for removing ground-off material producedduring the polishing process from the polishing pad.

[0033] According to the fifth aspect of the present invention, apolishing table for making predetermined motion; a top ring verticallymovably disposed above the polishing table for removably holding aworkpiece to be polished; a polishing pad supply device for holding anelongate polishing pad and supplying the polishing pad therefrom; apolishing pad holding device for holding the polishing pad supplied fromthe polishing pad supply device and placing the polishing pad such thatthe polishing pad make predetermined motion integrally with thepolishing table; and an atomizer for spraying gas-liquid mixture on thepolishing pad.

[0034] According to the sixth aspect of the present invention, apolishing table for making predetermined motion; a top ring verticallymovably disposed above the polishing table for removably holding aworkpiece to be polished; a polishing pad supply device for holding anelongate polishing pad and supplying the polishing pad therefrom; apolishing pad holding device for holding the polishing pad supplied fromthe polishing pad supply device and placing the polishing pad such thatthe polishing pad make predetermined motion integrally with thepolishing table; and an eddy-current sensor for monitoring thickness ofthe film of the workpiece.

[0035] According to the seventh aspect of the present invention, a firstpolishing table which mounts a polishing pad on the surface of the firstpolishing table, the polishing pad being held by at least two rollsdisposed around the first polishing table; and a second polishing tablewhich mounts a polishing pad on the surface of the second polishingtable, the polishing pad being held by at least two rolls disposedaround the second polishing table.

[0036] According to the eighth aspect of the present invention, a firstpolishing table which mounts a polishing pad on the surface of the firstpolishing table, the polishing pad being held by at least two rollsdisposed around the first polishing table; and a second polishing tablewhich mounts a polishing pad on the surface of the second polishingtable, the polishing pad being held by at least two rolls disposedaround the second polishing table, wherein respective shafts of therolls are substantially parallel to the polishing surface of thepolishing pad.

[0037] The above and other objects, features, and advantages of thepresent invention will become apparent from the following descriptionwhen taken in conjunction with the accompanying drawings whichillustrate a preferred embodiment of the present invention by way ofexample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIG. 1 is a front elevational view showing an essential part of apolishing apparatus according to a first embodiment of the presentinvention;

[0039]FIG. 2 is a plan view showing an essential part of the polishingapparatus according to the first embodiment of the present invention;

[0040]FIG. 3 is a front elevational view of the polishing apparatusshown in FIGS. 1 and 2 by additionally incorporating a dressingapparatus and the like;

[0041]FIG. 4 is a plan view of the polishing apparatus shown in FIGS. 1and 2 by additionally incorporating the dressing apparatus and the like;

[0042]FIG. 5 is a cross-sectional view showing the polishing pad, thepolishing table and the top ring;

[0043]FIG. 6 is a plan view showing the polishing pad, the polishing padand the polishing table in which sensors are embedded;

[0044]FIGS. 7A and 7B are graphs showing changes in the resonancefrequency of a detected signal that is produced by the eddy-currentsensor and processed by the controller while the substrate is beingpolished;

[0045]FIG. 8 is a cross-sectional view showing a polishing table and amotor section;

[0046]FIG. 9A is a plan view showing a section for supporting thepolishing table;

[0047]FIG. 9B is a cross-sectional view taken along line A-A of FIG. 9A.

[0048]FIG. 10 is a front elevational view showing an essential part of apolishing apparatus according to a second embodiment of the presentinvention;

[0049]FIG. 11 is a plan view showing an essential part of the polishingapparatus according to the second embodiment of the present invention;

[0050]FIG. 12 is a front elevational view showing an essential part of apolishing apparatus according to a third embodiment of the presentinvention;

[0051]FIG. 13 is a plan view showing an essential part of the polishingapparatus according to the third embodiment of the present invention;

[0052]FIG. 14 is a plan view showing a layout of various components of apolishing apparatus according to an embodiment of the present invention;

[0053]FIG. 15 is a view showing the relationship between the top ringand the polishing tables;

[0054]FIG. 16 is a front elevational view of a conventional polishingapparatus;

[0055]FIG. 17 is a plan view of the conventional polishing apparatusshown in FIG. 16;

[0056]FIG. 18 is a front elevational view of another conventionalpolishing apparatus; and

[0057]FIG. 19 is a front elevational view of still another conventionalpolishing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] Next, a polishing apparatus according to embodiments of thepresent invention will be described with reference to drawings.

[0059]FIGS. 1 and 2 show a polishing apparatus according to a firstembodiment of the present invention. As shown in FIGS. 1 and 2, apolishing apparatus according to the present invention comprises arectangular planar polishing table 10, a motor 12 for rotating thepolishing table 10, and a top ring 14 vertically movably disposed abovethe polishing table 10 for removably holding a substrate W such as asemiconductor wafer with its surface, to be polished, facing thepolishing table 10.

[0060] Support plates 16, 18 are attached to the lower surfaces ofopposite sides of the polishing table 10 and extend horizontally awayfrom each other from the opposite sides of the polishing table 10. Thesupport plate 16 supports a bearing 20 on its upper surface. An elongatesupply roll 22 has an end rotatably supported by the bearing 20, and anopposite end connected by a coupling 24 to a supply roll motor 26 thatis supported on the upper surface of the support plate 16. When thesupply roll motor 26 is energized, the supply roll 22 is rotated aboutits own axis. The other support plate 18 supports a bearing 28 on itsupper surface. An elongate take-up roll 30 has an end rotatablysupported by the bearing 28 and an opposite end connected by a coupling32 to a take-up roll motor 34 that is supported on the upper surface ofthe support plate 18. When the take-up roll motor 34 is energized, thetake-up roll 30 is rotated about its own axis.

[0061] An elongate polishing pad 36 is wound onto the supply roll 22,extends along the upper surface of the polishing table 10, and has afree end removably gripped by the take-up roll 30. When the supply rollmotor 26 and the take-up roll motor 34 are energized, the supply roll 22and the take-up roll 30 are synchronously rotated about their own axesin one direction to cause the polishing pad 36 to travel from the supplyroll 22 along the upper surface of the polishing table 10 toward thetake-up roll 30 onto which the polishing pad 36 is wound. The tension ofthe polishing pad 36 between the supply roll 22 and the take-up roll 30can be adjusted by regulating the rotational speeds of the supply roll22 and the take-up roll 30. The polishing pad 36 can be returned fromthe take-up roll 30 toward the supply roll 22 when the supply roll 22and the take-up roll 30 are reversed.

[0062] The polishing table 10 has an attraction section 40 forattracting the polishing pad 36 under vacuum to the upper surface of thepolishing table 10. The attraction section 40 comprises a plurality ofvacuum holes which are formed in the polishing table 10, and are open atthe upper surface of the polishing table 10 and connected to a vacuumsource such as a vacuum pump. A rotary joint 46 which connects a cable44 extending from a controller 42 and cables extending respectively fromthe supply roll motor 26 and the take-up roll motor 34 is attached tothe motor 12. The controller 42 controls the supply roll motor 26 andthe take-up roll motor 34, respectively through the cable 44 and thecables for motors. However, the controller 42 may be arranged to controlthe supply roll motor 26 and the take-up roll motor 34 in a wirelessfashion.

[0063] The polishing apparatus shown in FIGS. 1 and 2 operates asfollows: While the polishing table 10 and the top ring 14 are beingrotated independently about their own axes, the substrate W is pressedagainst the polishing pad 36 under a constant pressure by the top ring14, and a polishing liquid is supplied from a nozzle (not shown) to thepolishing pad 36, thereby polishing the surface of the substrate W to aflat mirror finish. At this time, the supply roll 22 and the take-uproll 30 also rotate about the axis of the polishing table 10 in unisonwith the polishing table 10. The polishing pad 36 is attracted to andheld by the upper surface of the polishing table 36 under vacuumdeveloped in the vacuum holes of the attraction section 40. Therefore,the polishing pad 36 is prevented from being displaced with respect tothe polishing table 10 while the substrate W is being polished thereby.

[0064] For polishing an oxide film on the substrate W, for example, thepolishing liquid comprises a silica slurry such as SS-25 (manufacturedby Cabbot), a CeO₂ slurry, or the like. For polishing a tungsten film onthe substrate W, for example, the polishing liquid comprises a silicaslurry such as W2000 (manufactured by Cabbot) containing an H₂O₂ as anoxidizing agent, an alumina-base slurry of iron nitrate, or the like.For polishing a copper film on the substrate W, for example, thepolishing liquid comprises a slurry containing an oxidizing agent, suchas H₂O₂ for turning the copper film into an oxide copper film, a slurryfor polishing a barrier layer, or the like. In order to remove particlesor defects from the substrate being polished, surfactant or alkalisolution as a polishing liquid may be supplied halfway for conducting afinish polishing.

[0065] The polishing pad 36 is made of polyurethane foam such as IC1000or a suede-like material such as Polytex. In order to increase theresiliency of the polishing pad 36, the polishing pad 36 may be linedwith a layer of nonwoven cloth or sponge, or a layer of nonwoven clothor sponge may be attached to the upper surface of the polishing table10.

[0066] The polishing pad 36 may comprise a fixed abrasive pad comprisingparticles of CeO₂, silica, alumina, SiC, or diamond embedded in abinder, so that the polishing pad 36 can polish the substrate W whilenot a polishing liquid containing abrasive particles but a polishingliquid containing no abrasive particles is being supplied thereto. Anammeter, a vibrometer, or an optical sensor may be incorporated in thepolishing table 10 and/or the top ring 14 for measuring the state of thesubstrate W while the substrate W is being polished.

[0067] When the region of the polishing pad 36 which has been used isworn to the extent that its polishing capability can no longer berestored by a dresser, the controller 42 sends a signal to energize thesupply roll motor 26 and the take-up roll motor 34 to rotate the supplyroll 22 and the take-up roll 30, respectively, in synchronism with eachother in one direction. Thus, the polishing pad 36 travels from thesupply roll 22 toward the take-up roll 30 along the upper surface of thepolishing table 10. After the polishing pad 36 has traveled apredetermined distance which is long enough to displace the worn regionof the polishing pad 36 off the upper surface of the polishing table 10,the controller 42 de-energizes the supply roll motor 26 and the take-uproll motor 34 to stop the supply roll 22 and the take-up roll 30, thuspositioning a new region of the polishing pad 36 over the upper surfaceof the polishing table 10.

[0068] Even when the polishing table 10 is in rotation, the worn regionof the polishing pad 36 can be automatically replaced with a new regionthereof by transporting the polishing pad 36 from the supply roll 22toward the take-up roll 30 over the upper surface of the polishing table10 by the predetermined distance corresponding to the length of thepolishing table 10, i.e. one pad and then stopping the polishing pad 36.Alternatively, the polishing pad 36 may be wound onto the take-up roll30 by the distance “a”, shown in FIGS. 1 and 2, corresponding thedistance from the end of the polishing table 10 to the center of thesubstrate W located at the polishing position. Thus, a new polishing padand a used polishing pad are simultaneously brought into connect withdifferent regions in a radial direction of the substrate W for therebyimparting a polishing action equally to the entire surface of thesubstrate W.

[0069] The polishing pad 36 and the supply roll 22 may be integrallycombined into a cartridge, so that they can be quickly installed andremoved between the bearing 20 and the coupling 24. The supply rollmotor 26 may be eliminated, and the polishing pad 36 may be suppliedfrom the supply roll 22 toward the take-up roll 30 only by the take-uproll motor 34. The polishing table 10 may be of a circular shape.

[0070]FIGS. 3 and 4 shows the polishing apparatus shown in FIGS. 1 and 2to which a dressing apparatus and the like are added. Specifically, thepolishing apparatus is provided with a diamond dresser 60 and a waterjet nozzle 65. The polishing liquid supply nozzle 70 denotes a polishingliquid supply nozzle for supplying a polishing liquid onto the centralarea of the polishing table 10. The diamond dresser 60 is angularlymovable in a horizontal plane between a dressing position over thepolishing table 10 and a standby position off the polishing table 10.The diamond dresser 60 has an electrodeposited diamond ring 61 whichcomprises fine grains of diamond electrodeposited on the lower surfacethereof. Specifically, the electrodeposoted diamond ring 61 is producedby attaching fine grains of diamond to its lower surface and thenplating its lower surface with nickel for thereby fixing the fine grainsof diamond with a plated nickel layer. The dresser 60 may be replacedwith an SiC dresser having a ring of sectors made of silicon carbide.The SiC dresser has on the surfaces of its sectors a number of pyramidalprojections each having a height of about several tens of μm.

[0071] On the other hand, the water jet nozzle 65 extends to the centralarea of the polishing pad 36 in a width direction of the polishing pad36, and has a plurality of openings disposed on its lower surface atcertain intervals for ejecting pure water jets therefrom. The water jetnozzle 65 is connected to a pump 66, and the pressure of the water jetsejected from the openings can be maintained in the range of 490 to 2940kPa (5 to 30 kg/cm²) by controlling the rotational speed of the pump 66.

[0072] With the above arrangement, the substrate W is polished bysupplying the polishing liquid containing abrasive particles from thepolishing liquid supply nozzle 70 onto the polishing pad 36, and thenfinish-polished by stopping the supply of the polishing liquid from thepolishing liquid supply nozzle 70 and supplying ultrapure water from thewater jet nozzle 65 onto the polishing pad 36. When the polishing pad 36starts to be used, it is first dressed by the diamond dresser 60 forinitial conditioning. Thereafter, the substrate W is polished using thedressed polishing pad 36. Between polishing processes, the polishing pad36 is dressed by the water jet nozzle 65 with water jets ejectedtherefrom.

[0073] Alternatively, when the polishing pad 36 starts to be used, it isfirst dressed by the diamond dresser 60 for initial conditioning.Thereafter, the substrate W is polished using the dressed polishing pad36. Between polishing processes, the polishing pad 36 is dressed in twosteps, i.e., first by the diamond dresser 60 and then by the water jetnozzle 65 with water jets ejected therefrom.

[0074] According to the polishing apparatus of the present invention,the finish-polishing can be conducted by supplying ultrapure water as apolishing liquid to the polishing pad 36 from the water jet nozzle 65.Further, after initial conditioning of the polishing pad 36 by thediamond dresser 60, polishing process of the substrate W is carried out,and after completing the polishing process, dressing of the polishingpad 36 with the water jet is carried out by the water jet nozzle 65.Thereafter, polishing process is carried out again. Further, betweenpolishing processes, dressing of the polishing pad 36 by the diamonddresser and the water jet may be combined.

[0075] In the illustrated embodiment, the contact-type dresser comprisesthe diamond dresser 60. However, the diamond dresser may be replacedwith a brush dresser.

[0076] Next, sensors provided in the polishing table for monitoring thestate of the substrate being polished will be described with referenceto FIGS. 5 through 7. FIG. 5 shows the polishing table and top ring incross-section. In FIG. 5, the polishing pad 36 is attached to thepolishing table 10 under vacuum.

[0077] As shown in FIG. 5, an eddy-current sensor 67 is mounted in thepolishing table 10, and is electrically connected to a controller 86 bya wire 84 extending through the polishing table 10, a table supportshaft 10 a, and a rotary connector or slip ring 85 mounted on the lowerend of the table support shaft 10 a. The controller 86 is connected to adisplay unit 87.

[0078] An optical sensor 75 is mounted in the polishing table 10adjacent to the eddy-current sensor 67. The optical sensor 75 comprisesa light-emitting element and a light-detecting element. Thelight-emitting element applies light to the surface, being polished, ofthe substrate W, and the light-detecting element detects reflected lightfrom the surface, being polished, of the substrate W. The polishing pad36 has an opening 36 c at a position corresponding to the optical sensor75. The optical sensor 75 is electrically connected to a controller 89by a wire 88 extending through the polishing table 10, the table supportshaft 10 a, the rotary connector 85 mounted on the lower end of thetable support shaft 10 a. The controller 89 is connected to the displayunit 87.

[0079] The top ring 14 is coupled to a motor (not shown) and connectedto a lifting/lowering cylinder (not shown). Therefore, the top ring 14is vertically movable and rotatable about its own axis, as indicated bythe arrows, and can press the substrate W against the polishing pad 36under a desired pressure. The top ring 14 is connected to the lower endof a vertical top ring drive shaft 73, and supports on its lower surfacean elastic pad 74 of polyurethane or the like. A cylindrical retainerring 69 is provided around an outer circumferential edge of the top ring14 for preventing the substrate W from being dislodged from the top ring14 while the substrate W is being polished.

[0080]FIG. 6 is a plan view showing the plating pad 36 and the polishingtable 10 in which the sensors are mounted. As shown in FIG. 6, theeddy-current sensor 67 and the optical sensor 75 are positioned so as topass through the center C_(W) of the substrate W held by the top ring 14while the substrate W is being polished, when the polishing table 10rotates about its own axis C_(T). While the eddy-current sensor 67 andthe optical sensor 75 pass along an arcuate path beneath the substrateW, the eddy-current sensor 67 and the optical sensor 75 continuouslydetect the thickness of a film such as a copper layer on the substrateW. In order to shorten the interval between detecting intervals, one ormore eddy-current sensors 67 and one or more optical sensors 75 may beadded as indicated by the imaginary lines in FIG. 6, so that at leasttwo sets of sensors are provided in the polishing table 10.

[0081] The polishing apparatus shown in FIG. 6 operates as follows: Thesubstrate W is held on the lower surface of the top ring 14, and pressedby the lifting/lowering cylinder against the polishing pad 36 on thepolishing table 10 which is rotating. The polishing liquid supply nozzle70 supplies the polishing liquid Q to the polishing pad 36 on thepolishing table 10, and the supplied polishing liquid Q is retained onthe polishing pad 36. The substrate W is polished in the presence of thepolishing liquid Q between the lower surface of the substrate W and thepolishing pad 36. While the substrate W is being thus polished, theeddy-current sensor 67 passes directly beneath the surface, beingpolished, of the substrate W each time the polishing table 10 makes onerevolution. Since the eddy-current sensor 67 is positioned on an arcuatepath extending through the center Cw of the substrate W, theeddy-current sensor 67 is capable of continuously detecting thethickness of the film on the substrate W as the eddy-current sensor 67moves along the arcuate path beneath the substrate W.

[0082] The principles of detecting the thickness of the film of copper,aluminum or the like on the substrate W with the eddy-current sensor 67will be described below.

[0083] The eddy-current sensor has a coil which is supplied with ahigh-frequency current. When the high-frequency current is supplied tothe coil of the eddy-current sensor, an eddy current is generated in thefilm on the substrate W. Since the generated eddy current variesdepending on the thickness of the film, the combined impedance of theeddy-current sensor and the film such as a copper layer is monitored todetect the thickness of the film. Specifically, the combined impedance Zof the eddy-current sensor and the copper layer is represented by theinductive and capacitive elements L, C of the eddy-current sensor, andthe resistive element R of the copper layer which is connected parallelto the inductive and capacitive elements L, C. When the resistiveelement R in the equation shown below varies, the combined impedance Zalso varies. At this time, the resonance frequency also varies, and arate of change of the resonance frequency is monitored to determine anend point of the CMP process.$Z = \frac{j\quad \omega \quad L}{\left( {1 - {\omega^{2}{LC}}} \right) + \frac{j\quad \omega \quad L}{R}}$

[0084] where Z: combined impedance, j: square root of −1 (imaginarynumber), L: inductance, f: resonance frequency, C: electrostaticcapacitance, R: resistance of the copper layer, ∫=2#f.

[0085]FIGS. 7A and 7B are graphs showing changes in the resonancefrequency of a detected signal that is produced by the eddy-currentsensor 67 and processed by the controller 86 while the substrate W isbeing polished. In FIGS. 7A and 7B, the horizontal axis representspolishing time, and the vertical axis represents the resonance frequency(Hz). FIG. 7A shows changes in the resonance frequency when theeddy-current sensor 67 passes a plurality of times directly below thesubstrate W, and FIG. 7B shows, at an enlarged scale, an encircledportion A in FIG. 7A. The result shown in FIGS. 7A and 7B is obtainedwhen the film on the substrate W is a copper layer.

[0086] As shown in FIG. 7A, as the polishing of the substrate Wprogresses, the value produced by processing the detected signal fromthe eddy-current sensor 67 is progressively reduced. This processing ofthe detected signal is performed by the controller 86. Specifically, asthe thickness of the copper layer decreases, the resonance frequencyobtained by processing the detected signal from the eddy-current sensor67 is progressively reduced. In FIG. 7A, the resonance frequencydecreases from an initial value of 6800 Hz. Therefore, if the value ofthe resonance frequency, at the time when the copper layer is removedexcept for the copper layer in the interconnection grooves, has beenexamined, then an end point of the CMP process can be detected bymonitoring the value of the resonance frequency. In FIG. 7A, the valueof the resonance frequency at the time when the copper layer is removedexcept for the copper layer in the interconnection grooves is 6620 Hz.If a certain frequency before reaching the end point of the CMP processis established as a threshold, then it is possible to polish thesubstrate W under a first polishing condition, then polish the substrateW under a second polishing condition after the threshold is reached, andfinish the CMP process when the end point thereof is reached by removingthe copper layer and the barrier layer completely.

[0087] Next, the principles of detecting the thickness of the copperlayer on the substrate W by the optical sensor 75 will be brieflydescribed.

[0088] During polishing, every time when the polishing table 10 makesone revolution, the optical sensor 75 passes along an arcuate pathbeneath the substrate W. Thus, light emitted from the light-emittingelement in the optical sensor 75 passes through the hole of thepolishing table 10 and the opening 36 c of the polishing pad 36 isincident on the surface, being polished, of the substrate W, and lightreflected from the surface of the substrate W is received by thelight-detecting element in the optical sensor 75. The light received bythe light-detecting element is processed by the controller 89 to measurethe thickness of the top layer on the substrate W.

[0089] The principles of detecting the thickness of the film by theoptical sensor utilizes the interference of light caused by the toplayer and a medium adjacent to the top layer. When light is applied tothe thin film on the substrate, a part of the light is reflected fromthe surface of the thin film while the remaining part of the light istransmitted through the thin film. A part of the transmitted light isthen reflected from the surface of the underlayer or the substrate,while the remaining part of the transmitted light is transmitted throughthe underlayer or the substrate. In this case, when the underlayer ismade of a metal, the light is absorbed in the underlayer. The phasedifference between the light reflected from the surface of the thin filmand the light reflected from the surface of the underlayer or thesubstrate creates the interference. When the phases of the two lightsare identical to each other, the light intensity is increased, whilewhen the phases of the two lights are opposite to each other, the lightintensity is decreased. That is, the reflection intensity varies withthe wavelength of the incident light, the film thickness, and therefractive index of the film. The light reflected from the substrate isseparated by a diffraction grating or the like, and a profile depictedby plotting the intensity of reflected light for each wavelength isanalyzed to measure the thickness of the film on the substrate.

[0090] By the polishing apparatus incorporating two kinds of the sensorsfor measuring the film thickness, until the thickness of the film suchas a copper layer is reduced to a certain smaller value, the thicknessof the film is monitored by the controller 86 which processes the signalfrom the eddy-current sensor 67. When the thickness of the film reachesthe certain smaller value and begins to be detected by the optionalsensor 75, the thickness of the thin film is monitored by the controller89 which processes the signal from the optical sensor 75. Therefore, byusing the optical sensor 75 which is of a higher sensitivity to thethickness of the copper layer (film), it is possible to accuratelydetect the time when the copper layer is removed except for the copperlayer in the interconnection grooves, thereby determining an end pointof the CMP process.

[0091] Alternatively, both the eddy-current sensor 67 and the opticalsensor 75 can be used until an end point of the CMP process is reached.Specifically, the controllers 86 and 89 process the respective signalsfrom the eddy-current sensor 67 and the optical sensor 75 to detect thetime when the copper layer is removed except for the copper layer in theinterconnection grooves, thereby determining an end of the CMP process.In the above embodiments, the film on the substrate W is made of copper.However, the film to be measured may comprise an insulating layer suchas SiO₂.

[0092] In the illustrated embodiments, the polishing table 10 is rotatedabout its own axis. However, the principles of the present invention arealso applicable to a polishing apparatus in which a polishing tablemakes circulatory motion, i.e. scroll motion.

[0093] Next, a polishing table which makes scroll motion will bedescribed with reference to FIG. 8 and 9. FIG. 8 is a cross-sectionalview showing a polishing table and a motor section, FIG. 9A is a planview showing a section for supporting the polishing table, and FIG. 9Bis a cross-sectional view taken along line A-A of FIG. 9A. In FIG. 8,the polishing pad 36 is held by a polishing table 130 under vacuum.

[0094] As shown in FIG. 8, a circular polishing table 130 is supportedby a cylindrical casing 134 which houses a drive motor 133 therein.Specifically, an annular support plate 135 extending radially inwardlyis provided at the upper part of the cylindrical casing 134, three ormore support sections 136 are formed in a circumferential direction onthe annular support plate 135, and the circular polishing table 130 issupported by these support sections 136. The support sections 136 andthe circular polishing table 130 have a plurality of recesses 138, 139,respectively in the upper and lower surfaces thereof at the positionsfacing to each other, which are arranged at circumferentially equalintervals, and bearings 140, 141 are fitted into the recesses 138, 139,respectively (see FIG. 9B). Connecting members 144 which have upper andlower shafts 142, 143 are provided in such a manner that the upper andlower shafts 142, 143 of each connecting member 144 are fitted into thebearings 140, 141, respectively.

[0095] The axis of the upper shaft 142 of the connecting member 144 isdisplaced from the axis of the lower shaft 143 by an eccentric distance“e” as shown in FIG. 9B, thereby allowing the polishing table 130 tomake circulative translation motion (scroll motion) along a circlehaving a radius “e”.

[0096] As shown in FIG. 8, a recess 148 is formed in the central area ofthe bottom surface of the polishing table 130 for accommodating a driveshaft 146 of a main shaft 145 through a bearing 147 fitted in the recess148. The axis of the drive shaft 146 is displaced from the axis of themain shaft 145 by an eccentric distance “e” as well. The drive motor 133is housed in a motor chamber 149 formed in the casing 134, and the mainshaft 145 of the drive motor 133 is supported by upper and lowerbearings 150, 151.

[0097] The polishing table 130 has a diameter slightly larger than thesum of twice the offset length “e” and the diameter of the substrate Wto be polished, and is constructed by joining two plate-like members153, 154. A space 155 is defined between the two plate-like members 153,154, and communicates with a vacuum source such as a vacuum pump and aplurality of vacuum holes 157 which are open at the upper surface of thepolishing table 130. Thus, when the space 155 communicates with thevacuum source, the polishing pad 36 is attracted to the polishing table130 under vacuum by the vacuum holes 157. The top ring (not shown) as apressing device has the same structure as those shown in FIGS. 1 and 5,except that this top ring rotates at a slower rotational speed.

[0098] With the above structure, while the polishing table 130 makesscroll motion and the top ring 14 (see FIGS. 1 and 5) is rotated aboutits own axis, the substrate W is pressed against the polishing pad 36under a constant pressure by the top ring 14 while the polishing liquidis supplied from the nozzle (not shown) onto the polishing pad 36,thereby polishing the surface of the substrate W to a flat mirrorfinish. At this time, the polishing pad 36 is attracted to and held bythe upper surface of the polishing table 130 under vacuum, and hence thepolishing pad 36 is prevented from being displaced with respect to thepolishing table 130 during polishing. The action of the minutecirculative translational motion (scroll motion) of radius “e” betweenthe substrate W and the polishing surface of the polishing pad 36produces a uniform polishing on the entire surface of the substrate W.If the positional relationship between the surface, to be polished, ofthe substrate W and the polishing surface of the polishing pad 36 is thesame, then the polished surface of the substrate is adversely influencedby local differences in the surface conditions of the polishing pad 36.In order to avoid such adverse influence, the top ring 14 is slowlyrotated about its own axis to prevent the surface of the substrate Wfrom being polished at the same position on the polishing pad 36.

[0099] Because the polishing table 130 shown in FIGS. 8 and 9 is ascroll motion type, the size of the polishing table 130 needs only to belarger than the size of the substrate W by the eccentric distance “e”.Therefore, the installation space required for installing the polishingtable is reduced significantly in comparison to the rotating-typepolishing table. Further, since the polishing table 130 makes scrollmotion, the polishing table 130 can be supported at a plurality ofpositions near the peripheral portion thereof as shown in FIG. 8, andhence the substrate can be polished to a higher degree of flatness incomparison with the rotation-type polishing table which rotates at ahigh speed.

[0100] The polishing table shown in FIGS. 8 and 9 may supply a polishingliquid onto the polishing surface of the polishing pad 36 through thepolishing table. In this case, the space 155 is connected to a polishingliquid supply source, and through-holes are formed in the polishing pad36 at positions corresponding to the holes 157 of the polishing table130. With this arrangement, the polishing liquid may be supplied ontothe upper surface of the polishing pad 36 through the space 155, theholes 157 and the through-holes of the polishing pad 36.

[0101]FIGS. 10 and 11 shows an essential part of a polishing apparatusaccording to a second embodiment of the present invention, and FIG. 10is a schematic cross-sectional view of the polishing apparatus and FIG.11 is a plan view of the polishing apparatus. As shown in FIG. 10, apolishing apparatus comprises a circular planar polishing table 10, amotor 12 for rotating the polishing table 10, and a top ring 14vertically movably disposed above the polishing table 10 for removablyholding a substrate W such as a semiconductor wafer with its surface, tobe polished, facing the polishing table 10. A support plate 16 isattached to a lower surface of the polishing table 10, and supports asupply roll 22 and a take-up roll 30 thereon through bearings 20, 28,respectively. The polishing table 10 is rotated about its own axis by adrive motor 12. While the substrate W is being polished, the take-uproll 30 is rotated by energizing a take-up roll motor 34 to cause thepolishing pad 36 to travel along the upper surface of the polishingtable 10 in a direction shown by an arrow. The polishing table 10 has afluid passage 10 c formed therein, and the fluid passage 10 c isconnected to a fluid source such as a compressed air source through arotary connector 85. The fluid passage 10 c is open at the upper surfaceof the polishing table 10, and when fluid is supplied to the fluidpassage 10 c, fluid such as a compressed air is ejected from the uppersurface of the polishing table 10.

[0102] With the above structure, during movement of the polishing pad36, fluid such as a compressed air is supplied to the fluid passage 10 cfrom the fluid source, and then the supplied fluid is ejected from theupper surface of the polishing table 10 toward the polishing pad 36.Thus, the frictional force between the polishing table 10 and thepolishing pad 36 is reduced, and the movement of the polishing pad 36along the polishing table 10, i.e. automatic replacement of thepolishing pad 36 can be smoothly conducted. When the pressure of fluidejected from the fluid passage 10 c toward the polishing pad 36 isvaried in accordance with the radial position of the substrate W, apressing force applied between the substrate W and the polishing pad 36can be changed at a central area and an outer circumferential area ofthe substrate W. Specifically, the polishing pressure applied to thesubstrate W can be varied in accordance with the positions in the radialdirection of the substrate W to thus control the polishing profile.

[0103] In FIG. 10, an air cylinder 51 for moving the top ring 14vertically, a swing arm 52 for angularly movably supporting the top ring14, and a motor 53 for angularly moving the swing arm 52 are shown.Further, a motor 54 for rotating the top ring 14 about its own axis isalso shown.

[0104] In the embodiment shown in FIG. 10, a sensor 55 for detecting asurface roughness of the polishing pad is provided downstream of thepolishing surface (the side of the take-up roll 30). In the sensor 55,light is applied to the polishing surface of the polishing pad 36 by alight-emitting element, reflected light from the polishing surface ofthe polishing pad 36 is received by a light-detecting element, and thesurface roughness of the polishing pad 36 is detected on the basis ofthe intensity of the reflected light received by the light-detectingelement. The sensor 55 is connected to a controller 56, and when thesensor 55 detects the wear of the polishing pad 36 and sends a signal tothe controller 56, the take-up roll motor 34 is energized to rotate thetake-up roll 30, and thus the polishing pad 36 is wound by apredetermined length. Further, a UV irradiating source 57 is providedbelow the polishing pad 36. In the case where the fixed abrasive pad isused, ultra violet ray is applied onto the polishing pad 36 from the UVirradiating source 57 to cause the binder for fixing abrasive particlesto deteriorate and to cause the abrasive particles of the polishing pad36 to be liberated.

[0105] According to this embodiment, the polishing pad 36 comprises aplurality of polishing pads which are divided in a longitudinaldirection thereof. Specifically, as shown in FIG. 11, two polishing pads36 a disposed at both sides and a polishing pad 36 b disposed at acentral portion are held by a common supply roll 22 and a common take-uproll 30, thus providing a plurality of polishing surfaces on thepolishing table 10. By moving the top ring 14 between the two kinds ofthe polishing pads 36 a, 36 b, when the substrate W held by the top ring14 is positioned at the central portion of the polishing table 10, thesubstrate W is polished only by the polishing pad 36 b, and when thesubstrate W held by the top ring 14 is positioned at the outerperipheral portion of the polishing table 10, the substrate W is mainlypolished by the polishing pad 36 a. According to the divided-typepolishing pads of the present invention, multi-stage polishing of thesubstrate W can be conducted under different conditions on a singlepolishing table. At this time, the rotational speed of the polishingtable 10 may be changed in the middle of polishing process, and thetake-up speed of the polishing pads 36 a, 36 b may be varied in themiddle of the polishing process. Further, the substrate W may bedisposed on the plurality of the polishing pads 36 a, 36 bsimultaneously, and the substrate W may be polished in such a mannerthat the substrate W is brought in contact with different polishing padsat the central portion and the outer peripheral portion of the substrateW.

[0106] The polishing liquid supply nozzle 70 extends over the polishingpads 36 a and 36 b, and has a plurality of openings at positionscorresponding to the polishing pads 36 a and 36 b so that a polishingliquid is supplied onto the polishing pads 36 a and 36 b simultaneously.A high-pressure pure water spray or atomizer 71 is disposed above thepolishing table 10 and adjacent to the polishing liquid supply nozzle 70so that high-pressure pure water or gas-liquid mixture (foggy mixture ofpure water and nitrogen) can be sprayed therefrom. Thus, high-pressurepure water or gas-liquid mixture is sprayed over the polishing surfaceby the high-pressure pure water spray or atomizer 71 for therebyconducting cleaning and dressing of the polishing surface. Further, abrush 72 having a nylon brush thereon may be provided to removeground-off material produced during the polishing process from thepolishing surface as a kind of a dressing process.

[0107] According to this embodiment, as shown in FIG. 11, a gap g isprovided between the polishing pad 36 a and the polishing pad 36 b.Thus, light emitted from the optical sensor 75 (see FIG. 5) comprising alight-emitting element and a light-detecting element mounted in thepolishing table 10 passes through the gap g between the polishing pad 36a and the polishing pad 36 b and is incident on the surface of thesubstrate W, and hence the thickness of the film on the substrate W canbe measured when the substrate W passes above the gap g between thepolishing pad 36 a and the polishing pad 36 b. After the thickness ofthe film on the substrate W measured by the optical sensor 75 reaches apredetermined value, the rotational speed of the top ring, therotational speed of the polishing table, and the pressing force appliedto the substrate W may be varied.

[0108] In the case where a thin polishing pad is used, medium such aslight, sound wave (acoustic emission), electromagnetic wave, or X-raypasses through the polishing pad, and hence by applying such medium tothe substrate W from the side of the polishing table, the thickness ofthe film on the substrate W can be measured.

[0109] Next, the structure of the components associated with thepolishing surface of the polishing pad 36 will be described below.

[0110] If ground-off material or fine particles produced by polishingare attached to the rolls or other rotating parts, the drive of suchrolls or parts are adversely affected. Thus, in the polishing apparatusof the present invention, the following measures are taken: the portionswhich are brought in sliding contact with each other are constructed bysynthetic resin; the portions which are brought in sliding contact witheach other are coated with synthetic resin; the portions from which dustis generated is exhausted; and the portions from which dust is generatedhas a labyrinth structure. With this arrangement, fine particles areprevented from being scattered, or from adhering to the drivingportions.

[0111] Further, the pressure in the polishing space in which thepolishing table, the polishing pad and the top ring are disposed is setsuch that the pressure decreases from high to low in the order of theposition where the substrate W to be polished is located, the polishingposition of the substrate W, and the position where the polishedsubstrate W is located.

[0112]FIGS. 12 and 13 show an essential part of a polishing apparatusaccording to a third embodiment of the present invention, and FIG. 12 isa schematic cross-sectional view and FIG. 13 is a plan view. In thepolishing apparatus of this embodiment, the polishing table 10 makeslinear reciprocating motion in a horizontal direction.

[0113] The polishing table 10 comprises a rectangular planar table, andthe polishing table 10 reciprocates linearly along a guide rail 80. Alinear motor 81 is provided at a portion which supports the polishingtable 10, and the polishing table 10 reciprocates along the guide rail80 by energizing the linear motor 81. A ball screw may be used insteadof the linear motor. The other construction of the polishing apparatusshown in FIGS. 12 and 13 is identical to the polishing apparatus shownin FIGS. 10 and 11. In the polishing apparatuses shown in FIGS. 10through 13, the polishing pad may be attracted under vacuum to thepolishing table.

[0114]FIG. 14 shows a whole structure of a polishing apparatus, andspecifically a layout of various components of the polishing apparatusaccording to the present invention. FIG. 15 shows the relationshipbetween the top ring 14 and the polishing tables 10 and 130. In thispolishing apparatus, the fixed abrasive pad and/or the polishing padmade of polyurethane foam or the like shown in FIGS. 1 though 13 whichcan be automatically replaced are used.

[0115] As shown in FIG. 14, a polishing apparatus according to thepresent invention comprises four load-unload stages 222 each for placinga wafer cassette 221 which accommodates a plurality of substrates W suchas semiconductor wafers. The load-unload stage 222 may have a mechanismfor raising and lowering the wafer cassette 221. A transfer robot 224having two hands is provided on rails 223 so that the transfer robot 224can move along the rails 223 and access the respective wafer cassettes221 on the respective load-unload stages 222.

[0116] The transfer robot 224 has two hands which are located in avertically spaced relationship, and the lower hand is used only fortaking out a substrate W from the wafer cassette 221 and the upper handis used only for returning the substrate W to the wafer cassette 221.This arrangement allows that a clean semiconductor wafer which has beencleaned is placed at an upper side and is not contaminated. The lowerhand is a vacuum attraction-type hand for holding a semiconductor waferunder vacuum, and the upper hand is a recess support-type hand forsupporting a peripheral edge of a semiconductor wafer by a recess formedon the hand. The vacuum attraction-type hand can hold a semiconductorwafer and transport the semiconductor wafer even if the semiconductorwafer is not located at a normal position in the wafer cassette due to aslight displacement, and the recess support-type hand can transport asemiconductor wafer while keeping the semiconductor wafer clean becausedust is not collected unlike the vacuum attraction-type hand. Twocleaning apparatuses 225 and 226 are disposed at the opposite side ofthe wafer cassettes 221 with respect to the rails 223 of the transferrobot 224. The cleaning apparatuses 225 and 226 are disposed atpositions that can be accessed by the hands of the transfer robot 224.Between the two cleaning apparatuses 225 and 226 and at a position thatcan be accessed by the transfer robot 224, there is provided a waferstation 270 having four wafer supports 227, 228, 229 and 230. Thecleaning apparatuses 225 and 226 have a spin-dry mechanism for drying asubstrate by spinning the substrate at a high speed, and hence thetwo-stage cleaning or three-stage cleaning of the substrate can beconducted without replacing any cleaning module.

[0117] An area B in which the cleaning apparatuses 225 and 226 and thewafer supports 227, 228, 229 and 230 are disposed and an area A in whichthe wafer cassettes 221 and the transfer robot 224 are disposed arepartitioned by a partition wall 284 so that the cleanliness of the areaB and the area A can be separated. The partition wall 284 has an openingfor allowing substrates W to pass therethrough, and a shutter 231 isprovided at the opening of the partition wall 284. A transfer robot 280having two hands is disposed at a position where the hands of thetransfer robot 280 can access the cleaning apparatus 225 and the threewafer supports 227, 229 and 230, and a transfer robot 281 having twohands is disposed at a position where the hands of the transfer robot281 can access the cleaning apparatus 226 and the three wafer supports228, 229 and 230.

[0118] The wafer support 227 is used to transfer a substrate W betweenthe transfer robot 224 and the transfer robot 280 and has a sensor 291for detecting whether there is a substrate W or not. The wafer support228 is used to transfer a substrate W between the transfer robot 224 andthe transfer robot 281 and has a sensor 292 for detecting whether thereis a substrate W or not. The wafer support 229 is used to transfer asubstrate W from the transfer robot 281 to the transfer robot 280, andhas a sensor 293 for detecting whether there is a substrate W or not andrinsing nozzles 295 for supplying a rinsing liquid to prevent asubstrate W from drying or to conduct rinsing of a substrate W. Thewafer support 230 is used to transfer a substrate W from the transferrobot 280 to the transfer robot 281, and has a sensor 294 for detectingwhether there is a substrate W or not and rinsing nozzles 296 forsupplying a rinsing liquid to prevent a substrate W from drying or toconduct rinsing of a substrate W. The wafer supports 229 and 230 aredisposed in a common water-scatter-prevention cover which has a openingdefined therein for transferring substrates therethrough, the openingbeing combined with a shutter 297. The wafer support 229 is disposedabove the wafer support 230, and the wafer support 229 serves to supporta substrate which has been cleaned and the wafer support 230 serves tosupport a substrate to be cleaned, so that the cleaned substrate isprevented from being contaminated by rinsing water which would otherwisefall thereon. The sensors 291, 292, 293 and 294, the rinsing nozzles 295and 296, and the shutter 297 are schematically shown in FIG. 14, andtheir positions and shapes are not illustrated exactly.

[0119] The transfer robot 280 and the transfer robot 281 have therespective two hands which are located in a vertically spacedrelationship. The respective upper hands of the transfer robot 280 andthe transfer robot 281 are used for transporting a substrate W which hasbeen cleaned to the cleaning apparatuses or the wafer supports of thewafer station 270, and the respective lower hands of the transfer robot280 and the transfer robot 281 are used for transporting a substrate Wwhich has not cleaned or a substrate W to be polished. Since the lowerhand is used to transfer a substrate to or from a reversing device, theupper hand is not contaminated by drops of a rinsing water which fallfrom an upper wall of the reversing device.

[0120] A cleaning apparatus 282 is disposed at a position adjacent tothe cleaning apparatus 225 and accessible by the hands of the transferrobot 280, and another cleaning apparatus 283 is disposed at a positionadjacent to the cleaning apparatus 226 and accessible by the hands ofthe transfer robot 281.

[0121] All the cleaning apparatuses 225, 226, 282 and 283, the wafersupports 227, 228, 229 and 230 of the wafer station 270, and thetransfer robots 280 and 281 are placed in the area B. The pressure inthe area B is adjusted so as to be lower than the pressure in the areaA. Each of the cleaning apparatuses 282 and 283 is capable of cleaningboth surfaces of a substrate.

[0122] The polishing apparatus has a housing 266 for enclosing variouscomponents therein. The interior of the housing 266 is partitioned intoa plurality of compartments or chambers (including the areas A and B) bypartitions 284, 285, 286 and 287.

[0123] A polishing chamber separated from the area B by the partitionwall 287 is formed, and is further divided into two areas C and D by thepartition wall 267. In each of the two areas C and D, there are providedtwo polishing tables, and a top ring for holding a substrate W andpressing the substrate W against the polishing tables. That is, thepolishing table 10 (see FIG. 1) and the polishing table 130 (see FIG. 8)are provided in the area C, and the polishing table 10 (see FIG. 1) andthe polishing table 130 (see FIG. 8) are provided in the area D.Further, the top ring 14 is provided in the area C and the top ring 14is provided in the area D. A polishing liquid supply nozzle 70 forsupplying a polishing liquid to the polishing table 10 in the area C anda dresser 60 (see FIG. 3) for dressing the polishing table 10 aredisposed in the area C. A polishing liquid supply nozzle 70 forsupplying a polishing liquid to the polishing table 10 in the area D anda dresser 60 (see FIG. 3) for dressing the polishing table 10 aredisposed in the area D. A dresser 268 for dressing the polishing table130 in the area C is disposed in the area C, and a dresser 269 fordressing the polishing table 130 in the area D is disposed in the areaD. The polishing tables 130 and 130 may be replaced with wet-typethickness measuring devices for measuring the thickness of a layer on asubstrate. If such wet-type thickness measuring devices are provided,then they can measure the thickness of a layer on a substrateimmediately after it is polished, and hence it is possible to furtherpolish the polished substrate or control a polishing process forpolishing a next substrate based on the measured value.

[0124] As shown in FIG. 14, in the area C separated from the area B bythe partition wall 287 and at a position that can be accessed by thehands of the transfer robot 280, there is provided a reversing device278 for reversing a semiconductor wafer, and at a position that can beaccessed by the hands of the transfer robot 281, there is provided areversing device 278′ for reversing a substrate W. The partition wall287 between the area B and the areas C, D has two openings each forallowing substrates to pass therethrough, one of which is used fortransferring the substrate W to or from the reversing device 278 and theother of which is used for transferring the substrate W to or from thereversing device 278′. Shutters 245 and 246 are provided at therespective openings of the partition wall 287.

[0125] The reversing devices 278 and 278′ have a chuck mechanism forchucking a substrate W, a reversing mechanism for reversing a substrateW, and a wafer detecting sensor for detecting whether the chuckmechanism chucks a substrate W or not, respectively. The transfer robot280 transfers a substrate W to the reversing device 278, and thetransfer robot 281 transfers a substrate W to the reversing device 278′.

[0126] As shown in FIGS. 14 and 15, a rotary transporter 277 is disposedbelow the reversing devices 278 and 278′ and the top ring 14 (in thearea C) and the top ring 14 (in the area D), for transferring substratesW between the cleaning chamber (area B) and the polishing chamber (areasC and D). The rotary transporter 277 has four stages for placingsubstrates W at equal angular intervals, and can hold a plurality ofsubstrates thereon at the same time.

[0127] The substrate W which has been transported to the reversingdevice 278 or 278′ is transferred to the lifter 279 or 279′ by actuatingthe lifter 279 or 279′ disposed below the rotary transporter 277 whenthe center of the stage of the rotary transporter 277 is aligned withthe center of the substrate W held by the reversing device 278 or 278′.The substrate W which has been transported to the lifter 279 or 279′ istransferred to the rotary transporter 277 by lowering the lifter 279 or279′. The substrate W placed on the stage of the rotary transporter 27is transported to a position below the top ring 14 (in the area C) orthe top ring 14 (in the area D) by rotating the rotary transporter 277by an angle of 90°. At this time, the top ring 14 (in the area C) or thetop ring 14 (in the are D) is positioned above the rotary transporter277 beforehand by a swing motion thereof.

[0128] The substrate W is transferred from the rotary transporter 277 tothe pusher 290 or 290′ and finally the substrate W is transferred to thetop ring 14 (in the area C) or the top ring 14 (in the are D) byactuating the pusher 290 or 290′ disposed below the rotary transporter277 when the center of the top ring 14 (in the area C) or the top ring14 (in the are D) is aligned with the center of the substrate placed onthe rotary transporter 277.

[0129] The substrate transferred to the top ring 14 (in the area C) orthe top ring 14 (in the are D) is held under vacuum by a vacuumattraction mechanism of the top ring, and transported to the polishingtable 10 (in the area C) or the polishing table 10 (in the area D).Thereafter, the substrate is polished by a polishing surface comprisinga polishing pad made of polyurethane foam or the like, or a fixedabrasive pad held by the polishing table 10. In the case where thepolishing pad made of polyurethane foam or the like and/or the fixedabrasive pad according to the present invention are used, a polishedsurface of the substrate having very few scratches can be obtained in afirst-stage polishing. The second polishing tables 130 and 130 aredisposed at positions that can be accessed by the top rings 14 and 14,respectively. With this arrangement, a primary polishing of thesubstrate W can be conducted by the first polishing table 10, and then afinish polishing of the substrate W is conducted by the finish polishingpad held by the second polishing table 130 or 130. In the finishpolishing table, the finish polishing of the substrate is conducted bythe polishing pad comprising SUBA400 or POLITEX (manufactured by RodelNitta) while supplying pure water onto the polishing pad or supplyingslurry onto the polishing pad. Alternatively, the primary polishing ofthe substrate can be conducted by the second polishing table 130 or 130,and then the secondary polishing of the semiconductor wafer can beconducted by the first polishing table 10 or 10. In this case, since thesecond polishing table has a smaller-diameter polishing surface than thefirst polishing table, a fixed abrasive pad which is more expensive thana polishing pad made of polyurethane foam or the like is attached to thesecond polishing table to thereby conduct a primary polishing of thesubstrate. On the other hand, the polishing pad made of polyurethanefoam or the like having a shorter life but being cheaper than the fixedabrasive pad is held by the first polishing table to thereby conduct afinish polishing of the substrate. This arrangement or utilization mayreduce the running cost of the polishing apparatus. If the polishing padmade of polyurethane foam or the like is held by the first polishingtable and the fixed abrasive pad is held by the second polishing table,then the polishing table system may be provided at a lower cost. This isbecause the fixed abrasive pad is more expensive than the polishing padmade of polyurethane foam or the like, and the price of the fixedabrasive pad is substantially proportional to the diameter of the fixedabrasive pad. Further, since the polishing pad made of polyurethane foamor the like has a shorter life than the fixed abrasive pad, if thepolishing pad is used under a relatively light load such as a finishpolishing, then the life of the polishing pad is prolonged. Further, ifthe diameter of the polishing pad is large, the chance or frequency ofthe contact with the substrate is distributed to thus provide a longerlife, a longer maintenance period, and an improved productivity of thesemiconductor devices.

[0130] As described above, according to one aspect of the presentinvention, even when the polishing table is in motion such as rotarymotion or circulatory motion, the polishing pad can be transported fromone of the rolls over the upper surface of the polishing table towardthe other roll by a distance corresponding a region of the polishing padthat has been used to polish workpieces. The used region of thepolishing pad can thus automatically be replaced with a new region ofthe polishing pad.

[0131] Further, according to another aspect of the present invention,the polishing pad is supplied from the polishing pad supply device, andthe supplied polishing pad is held by the polishing pad holding deviceand placed in a stretched state on the polishing table. Thus, even ifthe polishing table is in motion, the used region of the polishing padcan thus automatically be replaced with a new region of the polishingpad.

[0132] Although certain preferred embodiments of the present inventionhave been shown and described in detail, it should be understood thatvarious changes and modifications may be made therein without departingfrom the scope of the appended claims.

What is claimed is:
 1. A polishing apparatus comprising: a polishing table for making rotary or circulatory motion; a top ring vertically movably disposed above said polishing table for removably holding a workpiece to be polished; a pair of rolls rotatable about their own axes and movable in unison with said polishing table; and a polishing pad which is wound on one of said rolls and supplied over an upper surface of said polishing table toward the other of said rolls.
 2. A polishing apparatus according to claim 1, wherein said polishing table has an attraction section for attracting and holding the polishing pad to said polishing table.
 3. A polishing apparatus according to claim 1, further comprising a roll motor connected to at least said other of said rolls, said roll motor being controllable in a wireless or wired fashion.
 4. A polishing apparatus according to claim 1, wherein said polishing pad comprises one of a polyurethane foam pad, a suede type pad, and a fixed abrasive pad comprising abrasive particles embedded therein.
 5. A polishing apparatus according to claim 1, further comprising a sensor for detecting surface roughness of said polishing pad.
 6. A polishing apparatus according to claim 3, further comprising a sensor for detecting surface roughness of said polishing pad; and wherein said roll motor is energized on the basis of detection signal of said sensor.
 7. A polishing apparatus according to claim 1, wherein said polishing pad comprises a plurality of polishing pads which are divided along a take-up direction of said polishing pad.
 8. A polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above said polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; and a polishing pad holding device for holding the polishing pad supplied from said polishing pad supply device and placing the polishing pad such that the polishing pad make predetermined motion integrally with said polishing table.
 9. A polishing apparatus according to claim 8, wherein said polishing pad supply device comprises a supply roll onto which the elongate polishing pad is wound.
 10. A polishing apparatus according to claim 8, wherein said polishing pad holding device comprises a take-up roll onto which the elongate polishing pad is to be wound.
 11. A polishing apparatus according to claim 8, wherein said polishing table has an attraction section for attracting and holding the polishing pad to said polishing table.
 12. A polishing apparatus according to claim 10, further comprising a roll motor connected to said take-up roll, said roll motor being controllable in a wireless or wired fashion.
 13. A polishing apparatus according to claim 8, wherein said predetermined motion of said polishing table is one of rotary motion, circulatory motion, and linear reciprocating motion.
 14. A polishing apparatus comprising: a polishing table for making predetermined motion; and a top ring vertically movably disposed above said polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from said polishing pad supply device and placing the polishing pad such that the polishing pad make predetermined motion integrally with said polishing table; and a sensor for detecting surface roughness of the polishing pad.
 15. A polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above said polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from said polishing pad supply device and placing the polishing pad such that the polishing pad make predetermined motion integrally with said polishing table; and a brush for removing ground-off material produced during the polishing process from the polishing pad.
 16. A polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above said polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from said polishing pad supply device and placing the polishing pad such that the polishing pad make predetermined motion integrally with said polishing table; and an atomizer for spraying gas-liquid mixture on the polishing pad.
 17. A polishing apparatus comprising: a polishing table for making predetermined motion; a top ring vertically movably disposed above said polishing table for removably holding a workpiece to be polished; a polishing pad supply device for holding an elongate polishing pad and supplying the polishing pad therefrom; a polishing pad holding device for holding the polishing pad supplied from said polishing pad supply device and placing the polishing pad such that the polishing pad make predetermined motion integrally with said polishing table; and an eddy-current sensor for monitoring thickness of the film of the workpiece.
 18. A polishing apparatus comprising: a first polishing table which mounts a polishing pad on the surface of said first polishing table, said polishing pad being held by at least two rolls disposed around said first polishing table; and a second polishing table which mounts a polishing pad on the surface of said second polishing table, said polishing pad being held by at least two rolls disposed around said second polishing table.
 19. A polishing apparatus comprising: a first polishing table which mounts a polishing pad on the surface of said first polishing table, said polishing pad being held by at least two rolls disposed around said first polishing table; and a second polishing table which mounts a polishing pad on the surface of said second polishing table, said polishing pad being held by at least two rolls disposed around said second polishing table, wherein respective shafts of said rolls are substantially parallel to the polishing surface of said polishing pad. 